1. Field of the Invention
The present invention relates to a method of producing an ink ejection head.
2. Description of the Related Art
A typical example of a liquid droplet ejection head that ejects a liquid droplet is an ink ejection head to be applied to an inkjet recording system that ejects ink to a recording medium to perform recording. The ink ejection head generally includes an ink ejection orifice for ejecting the ink, a liquid chamber and an ink flow path communicating with the ink ejection orifice, and an energy-generating portion provided in the liquid chamber.
The ink ejection head performs recording by driving the energy-generating portion to eject an ink droplet from the ink ejection orifice. Accordingly, the size and shape of the ink ejection orifice affect ink ejection performance. In recent years, miniaturization of the ink ejection head has been progressing and an ultrafine ink ejection orifice capable of ejecting 5 pl or less of ink has been mounted on the ink ejection head.
However, when ink is stopped from being ejected over a long time period, a solvent in the ink vaporizes, and hence the ink thickens or solidifies to clog the inside of a fine ink ejection orifice in some cases. Accordingly, in order that ink having a high viscosity may be stably ejected, resistance of the ink at the time of its ejection needs to be reduced. The following has been known as one means for solving the problem. The ink ejection orifice is provided with a shape whose sectional area increases from an ink ejection orifice side to an ink ejection energy-generating element side (hereinafter referred to as “tapered shape”).
Japanese Patent Application Laid-Open No. 2007-320299 discloses a method of producing an ink ejection head having an ink ejection orifice of a tapered shape. A nozzle-forming member (hereinafter referred to as “nozzle”) formed of a negative photosensitive resist is applied onto a liquid chamber and flow path wall-molding material formed on a substrate. The nozzle has a two-layer structure and a latent image of a tapered shape is formed at the time of exposure by adding a light-absorbing material to a lower layer. An upper layer has sensitivity with which a latent image having constant dimensions with respect to mask dimensions at the time of the exposure can be formed. After the two layers have been stacked, collective exposure and development are performed. Thus, the ink ejection head having an ink ejection orifice of a tapered shape is obtained.